/*********************************************************************
 * Copyright (C) 2002 Andrew Khan
 * <p>
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * <p>
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * <p>
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ***************************************************************************/

package jxl.biff;

/**
 * Converts excel byte representations into integers
 */
public final class IntegerHelper {
    /**
     * Private constructor disables the instantiation of this object
     */
    private IntegerHelper() {
    }

    /**
     * Gets an int from two bytes
     *
     * @param b2 the second byte
     * @param b1 the first byte
     * @return The integer value
     */
    public static int getInt(byte b1, byte b2) {
        int i1 = b1 & 0xff;
        int i2 = b2 & 0xff;
        int val = i2 << 8 | i1;
        return val;
    }

    /**
     * Gets an short from two bytes
     *
     * @param b2 the second byte
     * @param b1 the first byte
     * @return The short value
     */
    public static short getShort(byte b1, byte b2) {
        short i1 = (short) (b1 & 0xff);
        short i2 = (short) (b2 & 0xff);
        short val = (short) (i2 << 8 | i1);
        return val;
    }


    /**
     * Gets an int from four bytes, doing all the necessary swapping
     *
     * @param b1 a byte
     * @param b2 a byte
     * @param b3 a byte
     * @param b4 a byte
     * @return the integer value represented by the four bytes
     */
    public static int getInt(byte b1, byte b2, byte b3, byte b4) {
        int i1 = getInt(b1, b2);
        int i2 = getInt(b3, b4);

        int val = i2 << 16 | i1;
        return val;
    }

    /**
     * Gets a two byte array from an integer
     *
     * @param i the integer
     * @return the two bytes
     */
    public static byte[] getTwoBytes(int i) {
        byte[] bytes = new byte[2];

        bytes[0] = (byte) (i & 0xff);
        bytes[1] = (byte) ((i & 0xff00) >> 8);

        return bytes;
    }

    /**
     * Gets a four byte array from an integer
     *
     * @param i the integer
     * @return a four byte array
     */
    public static byte[] getFourBytes(int i) {
        byte[] bytes = new byte[4];

        int i1 = i & 0xffff;
        int i2 = (i & 0xffff0000) >> 16;

        getTwoBytes(i1, bytes, 0);
        getTwoBytes(i2, bytes, 2);

        return bytes;
    }


    /**
     * Converts an integer into two bytes, and places it in the array at the
     * specified position
     *
     * @param target the array to place the byte data into
     * @param pos the position at which to place the data
     * @param i the integer value to convert
     */
    public static void getTwoBytes(int i, byte[] target, int pos) {
        target[pos] = (byte) (i & 0xff);
        target[pos + 1] = (byte) ((i & 0xff00) >> 8);
    }

    /**
     * Converts an integer into four bytes, and places it in the array at the
     * specified position
     *
     * @param target the array which is to contain the converted data
     * @param pos the position in the array in which to place the data
     * @param i the integer to convert
     */
    public static void getFourBytes(int i, byte[] target, int pos) {
        byte[] bytes = getFourBytes(i);
        target[pos] = bytes[0];
        target[pos + 1] = bytes[1];
        target[pos + 2] = bytes[2];
        target[pos + 3] = bytes[3];
    }
}
